This invention relates to a manually rotatable control or selector knob for electrical or electronic device such as a rotary switch, a volume control, etc. More particularly, this invention relates to a control or selector knob of the type which is capable of being locked in place at any desired angular position with respect to the forward end of a shaft extending from such electrical or electronic device thereby to be locked in a desired position with respect to the electrical or electronic device.
Such electrical or electronic devices are used for example in a radio receiver, a transceiver, etc. and have an operating shaft which cooperates with a knob member affixable thereto to form a rotatable assembly for volume controlling, or switch or selection operation of the electrical or electronic device. The operating shaft has forward end portion extending outside a housing or a panel of the electrical or electronic device and adapted to be received in a hole formed centrally in the knob member. The affixture of the knob member to the forward end portion of the operating shaft is conventionally attained by a screw inserted in the radial direction of the opening to abut the screw against the periphery of said forward end portion of the shaft. It is also conventional to provide, on the forward end portion of the shaft, a plurality of grooves or flutes extending along the length thereof and to form, on the inner periphery of the hole wall, a plurality of match or mating protuberances to be brought into mesh with said grooves when assembled for their interlocking. The latter method is more convenient than the former method because the former can achieve the affixture easily and quickly without using any special tool therefor and more advantageous because the knob member may be formed in any desired shape free from restriction due to the affixture with the screw. The method, however, has a fatal defect when used in such a case that the knob member should be mounted on the shaft accurately in place, keeping a predetermined relation to the electrical or electronic device to which the shaft is connected. Due to the fact that the interlocking or affixture between the knob member and the shaft is attained through the engagement of the grooves of the shaft and the mating protuberances of the opening of the knob, it is often difficult to lock the knob member in an accurate position or achieve fine adjustment with respect to the operational position of the electrical or electronic device. This defect is inherent in such locking through engagement between grooves and protuberances and cannot be eliminated completely even when the pitch of the grooves is reduced as small as possible. Stated illustratively, when an indicator knob having a pointer is required to be affixed to the shaft preliminarily connected, for example, to a rotary switch and mounted through a panel of the rotary switch, and the panel has on its front face indicia corresponding to the contact positions of the rotary switch, it is essential to dispose the pointer at an accurate relative position to the forward end portion of the shaft for accurate corresponding location with respect to the indicia of the panel and the contact positions of the rotary switch. If the pointer is not located in a proper position with reference to the contact positions of the rotary switch or the pointer is not accurately located on the corresponding indicia, not only the knob member but also the rotary switch should be unmounted from the panel for resetting. Such an inaccurate location of the knob member onto the shaft also provides a serious problem when the knob member has a board portion of increased diameter, for example for channel selector, and indicia are provided at its radial peripheral portion, because any disagreement from the desired position would be much amplified at the peripheral portion, causing more serious divergence from an indicator on a front panel as the diameter of the board portion increases. This defect would offset such advantage of the locking through groove-and-protuberance engagement as referred to above. In effect, it is not practical to employ this method in case where a knob member is mounted for a multicontact rotary switch and a plurality of indicia are provided closely with each other on an indication panel or a board portion of the knob member.
It is therefore an object of the present invention to provide a manually rotatable control or selector knob which is capable of being locked, by a simple operation, in place at any desired angular position with respect to the forward end of the operating shaft and therefore locked at any desired angular position with respect to the operational position of the electrical or electronic device.